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Title: Monte-Carlo simulations of Gunn diodes and hot-phonon effects in bulk semiconductors
Author: Appleyard, Nicholas
ISNI:       0000 0004 6423 0470
Awarding Body: University of Hull
Current Institution: University of Hull
Date of Award: 2016
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This thesis uses Monte Carlo simulations to investigate electron transport in GaAs, its ternary In0.₅₃Ga₀.₄₇As and GaN. Ensemble Monte Carlo methods are used to determine the effects of a non-equilibrium phonon distribution on the transport properties of bulk In₀.₅₃Ga₀.₄₇As. Hot phonons are shown to reduce the critical field, peak velocity and saturation velocity. The dominant hot phonon effects in In₀.₅₃Ga₀.₄₇As are shown to be diffusive heating and phonon re-absorption. Evidence of the phonon drag effect is not found. A notched GaAs Gunn diode originally modelled by J. Tully in 1983 [1] is then recreated with a finer mesh and more superparticles. The device is shown to operate in accumulation mode with a considerable ‘dead zone’. The model is shown to be consistent with the original to a reasonable estimate considering the uncertainty surrounding material parameters. Significantly less noise is present demonstrating the increased precision offered by a Monte Carlo model with an increased resolution. Characteristics of GaN Gunn diodes are then explored. Results are presented for a device operating in accumulation mode with an operating frequency of 164 GHz. Results are then presented for a device operating in dipole mode with an operating frequency of 119 GHz. The mechanisms surrounding the function of these devices are analysed and shown to be consistent with the literature. Finally, a proof of concept 2-dimensional device simulator is validated through comparison with an equivalent 1-dimensional device. While equivalency is proven a number of obstacles are highlighted surrounding computational efficiency and optimum simulation parameters.
Supervisor: Dyson, Angela Sponsor: Office of Naval Research, United States
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physics